openssl_verify

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

openssl_verify — Verify signature

Descrizione

openssl_verify() verifies that the signature is correct for the specified data using the public key associated with public_key. This must be the public key corresponding to the private key used for signing.

Elenco dei parametri

data

The string of data used to generate the signature previously

signature

A raw binary string, generated by openssl_sign() or similar means

public_key

OpenSSLAsymmetricKey - a key, returned by openssl_get_publickey()

string - a PEM formatted key (e.g. -----BEGIN PUBLIC KEY----- MIIBCgK...)

algorithm

int - one of these Signature Algorithms.

string - a valid string returned by openssl_get_md_methods() example, "sha1WithRSAEncryption" or "sha512".

Valori restituiti

Returns 1 if the signature is correct, 0 if it is incorrect, and -1 or false on error.

Log delle modifiche

Versione	Descrizione
8.0.0	`public_key` accepts an OpenSSLAsymmetricKey or OpenSSLCertificate instance now; previously, a resource of type `OpenSSL key` or `OpenSSL X.509` was accepted.

Esempi

Example #1 openssl_verify() example

<?php
// $data and $signature are assumed to contain the data and the signature

// fetch public key from certificate and ready it
$pubkeyid = openssl_pkey_get_public("file://src/openssl-0.9.6/demos/sign/cert.pem");

// state whether signature is okay or not
$ok = openssl_verify($data, $signature, $pubkeyid);
if ($ok == 1) {
    echo "good";
} elseif ($ok == 0) {
    echo "bad";
} else {
    echo "ugly, error checking signature";
}
// free the key from memory
openssl_free_key($pubkeyid);
?>

Example #2 openssl_verify() example

<?php
//data you want to sign
$data = 'my data';

//create new private and public key
$private_key_res = openssl_pkey_new(array(
    "private_key_bits" => 2048,
    "private_key_type" => OPENSSL_KEYTYPE_RSA,
));
$details = openssl_pkey_get_details($private_key_res);
$public_key_res = openssl_pkey_get_public($details['key']);

//create signature
openssl_sign($data, $signature, $private_key_res, "sha256WithRSAEncryption");

//verify signature
$ok = openssl_verify($data, $signature, $public_key_res, OPENSSL_ALGO_SHA256);
if ($ok == 1) {
    echo "valid";
} elseif ($ok == 0) {
    echo "invalid";
} else {
    echo "error: ".openssl_error_string();
}
?>

Vedere anche:

openssl_sign() - Generate signature

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User Contributed Notes 8 notes

down

Stiv ¶

18 years ago


I've finally found a way to verify signature. Sample in the documentation doesn't work. Code bellow DOES work :)

<?php
// $data is assumed to contain the data to be signed

// fetch certificate from file and ready it
$fp = fopen("path/file.pem", "r");
$cert = fread($fp, 8192);
fclose($fp);

// state whether signature is okay or not
// use the certificate, not the public key
$ok = openssl_verify($data, $signature, $cert);
if ($ok == 1) {
    echo "good";
} elseif ($ok == 0) {
    echo "bad";
} else {
    echo "ugly, error checking signature";
}
?>

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steve dot venable at lmco dot com ¶

22 years ago


A note about the openssl_verify() (and some of the other functions).  The public key comes from a certificate in any of the support formats (as the example shows, use openssl_get_publickey() to get the resource id).  But after some trial and error I found the signature string MUST BE BINARY.  While no error occurs, passing a base64-formatted signature string (PEM format?), you simply get a mismatch.  When I did the base64 decode myself, the verify returned a match (return value 1).  You can simply drop the begin/end lines and take the output of the 'base64_decode()' function.

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mikey at badpenguins dot com ¶

14 years ago


I spent days scouring the php openssl documentation trying to figure out how to do what sounds like a simple task - given two PEM encoded certificates, is one the signer of the other?  Nowhere in the openssl_verify() documentation or comments is it explained where to obtain the signature of an existing certificate.  The openssl_x509_parse() function looked promising, but it is an unstable API that may change.

I had to write my own code to determine if one cert signed another, it is located here: http://badpenguins.com/source/misc/isCertSigner.php?viewSource

In a nutshell here is what I learned...

The signature data in a signed X.509 certificate contains DER formatted data about the signature that is encrypted with the signers public key.  The data contains a hash of the original subject certificate and information about what encryption algorithm was used to create the signature.

So you need to get this signature data and a copy of the original certificate with the issuer and signature sequences removed.  Hash a copy of the original certificate (sans issuer/signature sequences) with the same algorithm the issuer used and if the hashes match, you have the issuer cert that signed the certificate.

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phpdev at fpierrat dot fr ¶

3 years ago


As stated from the doc: "Returns 1 if the signature is correct, 0 if it is incorrect, and -1 or false on error. "

In the second example as a well as in Stiv's note, following condition will match for both 0 or false, which have different meaning:
elseif ($ok == 0) {
    echo "bad";
}

On should do an identical test here (===) instead of an equal test (==):
elseif ($ok === 0) {
    echo "bad";
}
---
var_dump(0==false); //==> true
var_dump(0===false);//==> false

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peter dot labos at gmail dot com ¶

6 years ago


openssl_verify() is populating openssl_error_string() even on false. 

When openssl_verify() returns 0, openssl_error_string() is populated with 1.
I spent lot of time to understand, while my next call to openssl was failing with checks for error.

<?php
$c = file_get_contents($filename);
$publicKey = openssl_pkey_get_public($c);
$result = openssl_verify('freedom', 'someirrelevantnosign', $publicKey);

$error = "";

while ($msg = openssl_error_string() !== false) {
    $error .= $msg;
}

if (!empty($error)) {
    echo $error; // 1
}

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meint dot post at bigfoot dot com ¶

23 years ago


Anbybody trying to get a Win32 CryptoAPI based digital signature component to work with the openssl_verify() function should be aware that the CryptoAPI PKCS1 (RSA) method uses bytes in reverse order while the openssl_verify() method expects a correctly formatted PKCS1 digital signature (as should be). I learned this the hard way and it took me some time to dig this out. A simple solution in VBScript to reverse the byte order:



N = Len(Blob.Hex)



' reverse bytes in the signature using Hex format 

For i = 1 To N - 1 Step 2 

    s = Mid(Blob, i, 2) & s 

Next 



s contains the digital signature in reverse order. Blob is an arbitrary binary container.



Send the signature off in Hex format and use a hex2bin method in PHP to convert to the correct format for openssl_verify(), i.e.



function hex2bin($data) {



    $len = strlen($data);

    return pack("H" . $len, $data);



} 



That's it, hope it helps out. BTW I used ASPEncrypt to toy around with on Win32 platform. Works only with Internet Explorer but you could also use a Java applet and have none of the abovementioned problems :-)

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-1

attila dot m dot magyar at gmail dot com ¶

10 years ago


mikey at badpenguins dot com -- validating an X509 certificate chain in php seems to be possible with openssl_x509_checkpurpose()

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-1

jeremie dot gomez at gmail dot com ¶

13 years ago


You can actually use the public key as third parameter and not the certificate.

If you can't make it work, make sure that :

1) Your public key is well formatted. It seems that it must have the ----BEGIN PUBLIC KEY---- and ----END PUBLIC KEY----

2) Your signature is in binary format. You can use the php base64_decode for this.

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